The present invention relates to a two-legged body comprising two legs, an oscillation element and a connecting element for the mutual coupling of the legs and the oscillation element, wherein the legs are pivotable in relation to the-connecting element and during operation undergo a reciprocating angular displacement in relation to the connecting element, depending on the oscillation element.
U.S. Pat. No.1,599,290 discloses a body with four legs that are pivotably attached to a frame, and wherein oscillation elements in the form of springs are connected to the legs to cause the body to perform a walking motion.
A two-legged body according to the preamble of the main claim is known from the European patent application EP-A-0 531 731. The known device comprises two legs which are pivotably fastened at their top end to a horizontally oriented axis and in which each leg at its other end is provided with a foot having an arched surface. The known body is further provided with a pendulum also fastened to the axis, which can be made to oscillate and which in association with a traction force exerted on the known body, is able to provide the body with a movement by reciprocally moving its legs in counter phase, so that the two-legged body makes a walking movement.
A first disadvantage of the known two-legged body is that for the locomotion it is necessary to provide a separate traction force, as the oscillatory motion only suffices to cause the reciprocal movement of the two lets of the body. If such a force is not supplied separately, it can be provided by placing the known body on a sloping surface, so that the known body is provided with a force component in the horizontal plane, thereby allowing the body to move. A second disadvantage of the known two-legged body is that the walking movement is decided once the geometry of the body has been chosen.
The object of the invention is to provide a two-legged body that is able to carry out a walking movement without requiring the provision of a traction force other than the oscillatory motion, in such a manner, that the energy for locomotion is derived from the autonomous oscillation energy.
To this end the two-legged body according to the invention is characterized in that the oscillation element comprises at least two springs for the generation of antagonistic forces, that the springs are coupled at one side with a leg, and that together with the mass present in the body they are able to form a vibrating mass-spring system, and that the spring stiffness of at least one spring is adjustable. By this measure a two-legged body is provided with legs whose reciprocal movement from which the walking movement is derived, is to a large extent adjustable. The adjustment or alteration of the spring stiffness directly influences the frequency at which the mass-spring system preferentially vibrates. In addition, the alteration of the spring stiffness gives impetus to the mass-spring system, so that such an alteration produces energy from which the locomotive energy of the body can be derived. The amplitude of the vibration of the mass-spring system is also determined by the measure in which the spring stiffness is altered during operation. A large number of aspects of the two-legged body according to the invention can be controlled in this way without the need to provide motors and servo systems which are known as such, for the realization of the desired contollability. Due to the fact that such provisions may be absent, the known two-legged body can be embodied such as to be relatively light, thereby limiting the energy requirements and making the two-legged body very suitable for robotic and rehabilitation purposes. It should be noted that the body according to the invention can also be constructed with only one spring, in such a manner that to provide the antagonistic force for the spring, use is made of the gravitational force. However, compared with the embodiment with two springs. such a construction appears to be less flexible.
A workable embodiment producing a locomotive rhythm that for two-legged bodies appears very natural is characterized in that at the side facing away from the coupling with the leg, each of the springs is coupled with the connecting element, and that the springs are arranged at both sides of the leg.
This may be realized particularly simply if the connecting element is embodied with a cylindrical rotating spool, via which rotating spool a connecting cable or strip is led which is connected at both its ends with the two springs.
The locomotion of the two-legged body according to the invention may be suitably advanced by an embodiment in which each of the legs is mounted on an individual auxiliary frame, auxiliary frame is rotatably mounted on the connecting element, and each leg is adjustable in the longitudinal direction of its auxiliary frame. This provides the two-legged body, again in a natural manner, with a propelling force the moment the reciprocal movement of the respective leg is virtually completed but is still just in contact with the supporting surface from which the leg can push off.